Many telephone systems, particularly cordless telephone systems, are designed to operate in urban environments which have a high level of ambient noise. Conditions of this type make the optimization of sidetone level extremely important. In telephony, sidetone is defined as an attenuated level of one's own voice heard in the telephone handset ear piece. In telephony systems in which there is a delay to the audio path, the sidetone produced by the 4 wire to 2 wire reflection will sound like an echo. This echo can be annoying to the user to the point of disrupting his ability to communicate on the telephone. To overcome this problem, echo cancelers, usually digital signal processors, are used to dynamically reduce the reflected echoes or sidetones. These echo cancelers need a certain amount of time to converge which results in the sidetone being heard for a certain amount of time.
The echo canceler can train on near end audio, white noise, or background noise. Typically the training of the echo canceler begins once communication between a near end and far end user has been established. If audio is used, it results in the near end user initially hearing his sidetone, then gradually hearing the sidetone dissipate. When background noise is used, the low levels of background noise cause the echo canceler to take longer to converge, resulting in an increased chance that the near end user will begin speaking before convergence. This in turn results in the near end user initially hearing his sidetone as the canceler converges. If the noise level is increased to a level higher than the background noise, the far end user may hear the added noise for the duration of the training of the canceler.
Hence, there is a need for an improved method for reducing sidetone in a communication device.